docs: def validate():
      """Validate metadata content.
      ---
      tags:
        - ddo
      consumes:
        - application/json
      parameters:
        - in: body
          name: body
          required: true
          description: Asset metadata.
          schema:
            type: object
      responses:
        200:
          description: successfully request.
        500:
          description: Error
      """
      assert isinstance(request.json, dict), 'invalid payload format.'
      data = request.json
      assert isinstance(data, dict), 'invalid `body` type, should be formatted as a dict.'
      if is_valid_dict(data):
          return jsonify(True)
      else:
          error_list = list()
          for err in list_errors_dict_local(data):
              stack_path = list(err[1].relative_path)
              stack_path = [str(p) for p in stack_path]
              this_err_response = {'path': "/".join(stack_path), 'message': err[1].message}
              error_list.append(this_err_response)
          res = jsonify(error_list)
          return res